A common strategy towards the synthesis of 1,4-dideoxy-1,4-imino-l-xylitol, deacetyl (+)-anisomycin and amino-substituted piperidine iminosugars.

A strategy towards the synthesis of three different target molecules, namely 1,4-dideoxy-1,4-imino-l-xylitol, deacetyl (+)-anisomycin and amino-substituted piperidine iminosugars, molecules of potential biological and medicinal significance, is reported from a common amino-vicinal diol intermediate derived from tri-O-benzyl-d-glucal. Construction of the key pyrrolidine ring present in 1,4-dideoxy-1,4-imino-l-xylitol and (+)-anisomycin was a consequence of thermodynamically driven concomitant intramolecular nucleophilic addition reaction of the amino group to the resultant aldehyde obtained by oxidative cleavage of the amino-vicinal diol. Alternatively, double nucleophilic substitution on an amino-diol, after mesylation, with various amines delivered amino-substituted piperidine iminosugars in good yields.

Synthesis of natural deep eutectic solvents using a mixture design for extraction of animal and plant samples prior to ICP-MS analysis.

Solvents with both low density and viscosity have the advantage of higher extraction efficiency due to lower diffusivity and consequently higher mass transfer. In this study, a mixture design was performed for the synthesis of three different natural deep eutectic solvents (NADES) using citric acid, malic acid, and xylitol. The optimized proportion for each of the three solvents synthesized was selected based on density and viscosity values. The NADES were characterized by infrared spectroscopy analysis, that showed characteristic bands of the initial reagents and the presence of hydrogen bonds confirming the formation of each deep eutectic solvent. Then, the NADES were used as solvents in ultrasound-assisted extraction (UAE) and microwave-assisted extraction (MAE) of biological tissue and plant material samples for the determination of As, Cd, Hg, Pb, Se, and V by inductively coupled plasma mass spectrometry (ICP-MS). The results for the proposed methods were compared to microwave-assisted acid digestion (MW-AD). The extraction recoveries ranged from 80 to 120% for most of the elements determined. The use of NADES as carbon sources improved the sensitivity of the As and Cd analyses, due to charge transfer reactions between the analyte and C+ and/or other carbon species. In addition, the Analytical Eco-Scale was used to assess the greenness of the proposed analytical procedures (UAE and MAE). It showed that the UAE and MAE methods provided excellent green analyses, while the MW-AD method was rated as an acceptable green procedure.

Effect of processing methods on xylitol-starch base co-processed adjuvant for orally disintegrating tablet application.

Orally disintegrating tablet (ODT) is a friendly dosage form that requires no access to water and serves as a solution to non-compliance. There are many co-processed adjuvants available in the market. However, there is no single product possesses all the ideal characteristics such as good compressibility, fast disintegration and good palatability for ODT application. The aim of this research was to produce a xylitol-starch base co-processed adjuvant which is suitable for ODT application. Two processing methods namely wet granulation and freeze drying were used to compare the characteristics of co-processed adjuvant comprising of xylitol, starch and crospovidone XL-10 mixed at various ratios. The co-processed excipients were compressed into ODT and physically characterized for powder flow, particle size, hardness, thickness, weight, friability, in-vitro disintegration time and in-situ disintegration time, lubricant sensitivity, dilution potential, Fourier transform infrared spectroscopy, scanning electronic microscopy and x-ray diffraction analysis. Formulation F6 was selected as the optimum formulation due to the fastest in-vitro (135.33±11.52 s) and in-situ disintegration time (88.67±13.56s) among all the formulations (p<0.05). Increase in starch component decreases disintegration time of ODT. The powder flow fell under the category of fair flow. Generally, it was observed that freeze drying method produced smaller particle size granules compared to wet granulation method. ODT produced from freeze drying method had shorter disintegration time compared to ODT from wet granulation batch. In conclusion, a novel co-processed excipient comprised of xylitol, starch and crospovidone XL-10, produced using freeze drying method with fast disintegration time, good compressibility and palatability was developed and characterized. The co-processed excipient is suitable for ODT application.

Natural deep eutectic solvents for sample preparation prior to elemental analysis by plasma-based techniques.

Natural deep eutectic solvents (NADES) based on xylitol, citric acid, and malic acid were synthesized and were then characterized using infrared spectroscopy, thermogravimetry (TG), differential scanning calorimetry (DSC), also density and viscosity were measurements. The deep eutectic solvents were used as solvent in ultrasound-assisted extraction (DES-UAE) of plant samples prior to elemental analysis. Inductively coupled plasma-mass spectrometry (ICP-MS) and inductively coupled plasma-optical emission spectrometry (ICP OES) were employed for the determination of As, Ca, Cd, Cu, Fe, K, Mg, Mn, Na, P, and Zn in the extracts. The infrared analyses of the NADES revealed bands characteristic of the initial reagents, with the presence of hydrogen bonds, which confirmed the formation of a NADES. The thermal analyses showed decomposition temperatures of around 170 °C and endothermic events related to degradation of the NADES. The viscosity and density parameters were found to be related to the presence of hydrogen bonds. The extraction recoveries ranged from 80% to 120%, with some analytes presenting poor recoveries. There were no significant differences between the NADES, in terms of the concentrations of the analytes found in the extracts. However, there were differences between the analyte concentrations obtained using the NADES extraction method and the concentrations obtained using microwave-assisted acid digestion (MW-AD), possibly due to the different types of interactions between the solvents and the analytes. Plant tissues are complex matrices containing substantial amounts of silica, so some elements may be tightly bound and consequently difficult to release. The results indicated that UAE using NADES is a promising technique for the elemental extraction of plant samples.

Stereodivergent synthesis of right- and left-handed iminoxylitol heterodimers and monomers. Study of their impact on ß-glucocerebrosidase activity.

A library of dimers and heterodimers of both enantiomers of 2-O-alkylated iminoxylitol derivatives has been synthesised and evaluated on ß-glucocerebrosidase (GCase), the enzyme responsible for Gaucher disease (GD). Although the objective was to target simultaneously the active site and a secondary binding site of the glucosidase, the (-)-2-iminoxylitol moiety seemed detrimental for imiglucerase inhibition and no significant enhancement was obtained in G202R, N370S and L444P fibroblasts. However, all compounds having at least one (+)-2-O-alkyl iminoxylitol are GCase inhibitors in the nano molar range and are significant GCase activity enhancers in G202R fibroblats, as confirmed by a decrease of glucosylceramide levels and by co-localization studies.

N-Guanidino Derivatives of 1,5-Dideoxy-1,5-imino-d-xylitol are Potent, Selective, and Stable Inhibitors of ß-Glucocerebrosidase.

A series of lipidated guanidino and urea derivatives of 1,5-dideoxy-1,5-imino-d-xylitol were prepared from d-xylose using a concise synthetic protocol. Inhibition assays with a panel of glycosidases revealed that the guanidino analogues display potent inhibition against human recombinant ß-glucocerebrosidase with IC50 values in the low nanomolar range. Related urea analogues of 1,5-dideoxy-1,5-imino-d-xylitol were also synthesized and evaluated in the same fashion and found to be selective for ß-galactosidase from bovine liver. No inhibition of human recombinant ß-glucocerebrosidase was observed for the urea analogues. Computational studies provided insight into the potent activity of analogues bearing the substituted guanidine moiety in the inhibition of lysosomal glucocerebrosidase (GBA).

Synthesis of Xylitan Derivatives and Preliminary Evaluation of in Vitro Trypanocidal Activity.

A series of novel xylitan derivatives derived from xylitol were synthesized using operationally simple procedures. A xylitan acetonide was the key intermediate used to prepare benzoate, arylsulfonate esters and 1,2,3-triazole derivatives of xylitan. These compounds were evaluated for their in vitro anti-Trypanosoma cruzi activity against trypomastigote and amastigote forms of the parasite in T. cruzi-infected cell lineages. Benznidazole was used as positive control against T. cruzi and cytotoxicity was determined in mammalian L929 cells. The arylsulfonate xylitan derivative bearing a nitro group displayed the best activity of all the compounds tested, and was slightly more potent than the reference drug benznidazole. The importance of the isopropylidene ketal moiety was established and the greater lipophilicity of these compounds suggests enhancement in cell penetration.

Glucocerebrosidase enhancers for selected Gaucher disease genotypes by modification of α-1-C-substituted imino-D-xylitols (DIXs) by click chemistry.

A series of hybrid analogues was designed by combination of the iminoxylitol scaffold of parent 1C9-DIX with triazolylalkyl side chains. The resulting compounds were considered potential pharmacological chaperones in Gaucher disease. The DIX analogues reported here were synthesized by CuAAC click chemistry from scaffold 1 (α-1-C-propargyl-1,5-dideoxy-1,5-imino-D-xylitol) and screened as imiglucerase inhibitors. A set of selected compounds were tested as ß-glucocerebrosidase (GBA1) enhancers in fibroblasts from Gaucher patients bearing different genotypes. A number of these DIX compounds were revealed as potent GBA1 enhancers in genotypes containing the G202R mutation, particularly compound DIX-28 (α-1-C-[(1-(3-trimethylsilyl)propyl)-1H-1,2,3-triazol-4-yl)methyl]-1,5-dideoxy-1,5-imino-D-xylitol), bearing the 3-trimethylsilylpropyl group as a new surrogate of a long alkyl chain, with approximately threefold activity enhancement at 10 nM. Despite their structural similarities with isofagomine and with our previously reported aminocyclitols, the present DIX compounds behaved as non-competitive inhibitors, with the exception of the mixed-type inhibitor DIX-28.

Synthesis of the enantiomers of XYLNAc and LYXNAc: comparison of ß-N-acetylhexosaminidase inhibition by the 8 stereoisomers of 2-N-acetylamino-1,2,4-trideoxy-1,4-iminopentitols.

The enantiomers of XYLNAc (2-N-acetylamino-1,2,4-trideoxy-1,4-iminoxylitol) are prepared from the enantiomers of glucuronolactone; the synthesis of the enantiomers of LYXNAc (2-N-acetylamino-1,2,4-trideoxy-1,4-iminolyxitol) from an L-arabinono-δ-lactone and a D-ribono-δ-lactone is reported. A comparison is made of the inhibition of ß-N-acetylhexosaminidases (HexNAcases) and α-N-acetylgalactosaminidase (α-GalNAcase) by 8 stereoisomeric 2-N-acetylamino-1,2,4-trideoxy-1,4-iminopentitols; their N-benzyl derivatives are better inhibitors than the parent compounds. Both XYLNAc and LABNAc are potent inhibitors against HexNAcases. None of the compounds show any inhibition of α-GalNAcase.

Short synthesis of 3-(hydroxymethyl)xylitol and structure revision of the anti-diabetic natural product from Casearia esculenta.

3-(Hydroxymethyl)xylitol, a compound reportedly isolated from the root of Casearia esculenta (Roxb.), along with its three possible stereoisomers, has been synthesized for the first time by way of a triple dihydroxylation reaction performed upon the simplest cross-conjugated hydrocarbon, [3]dendralene. The data for the natural product do not match any of the isomeric 3-(hydroxymethyl)pentitols. The structure of the natural product from the root of Casearia esculenta (Roxb.) has been corrected by reanalysis of the published data.

Xylitol production from corncob hydrolysate using polyurethane foam with immobilized Candida tropicalis.

Polyurethane foam (PUF) was used as a carrier for Candida tropicalis (C. tropicalis) in the multi-batches fermentation of xylitol from xylose-containing corncob hemicellulose hydrolysate. After washing and sterilization, PUF (density of 320 kgm(-3), specific surface area of 1.5-2.0 × 10(5) m(2) m(-3), average porosity of 95%, pore diameter of 0.03 mm and cubic length of 5mm) was mixed with the culture medium at appropriate proportion followed by the inoculation. The fermentation parameters such as initial cell concentration, PUF dosage, pH value and temperature were controlled to study the effects on xylitol fermentation. In the 21-day durability tests, the optimal xylitol yield and volumetric productivity reached to 71.2% and 2.10 gL(-1)h(-1) respectively. Moreover, the average xylitol yield and volumetric productivity were 66.3% and 1.90 gL(-1)h(-1) for ten batchwise operations. The current research demonstrated that the PUF immobilization could serve as an efficient method for improving the cells vitality and enzyme reactivity in the continuous operation of fermentation.

Rapid assembly of a library of lipophilic iminosugars via the thiol-ene reaction yields promising pharmacological chaperones for the treatment of Gaucher disease.

A highly divergent route to lipophilic iminosugars that utilizes the thiol-ene reaction was developed to enable the rapid synthesis of a collection of 16 dideoxyiminoxylitols bearing various different lipophilic substituents. Enzyme kinetic analyses revealed that a number of these products are potent, low-nanomolar inhibitors of human glucocerebrosidase that stabilize the enzyme to thermal denaturation by up to 20 K. Cell based assays conducted on Gaucher disease patient derived fibroblasts demonstrated that administration of the compounds can increase lysosomal glucocerebrosidase activity levels by therapeutically relevant amounts, as much as 3.2-fold in cells homozygous for the p.N370S mutation and 1.4-fold in cells homozygous for the p.L444P mutation. Several compounds elicited this increase in enzyme activity over a relatively wide dosage range. The data assembled here illustrate how the lipophilic moiety common to many glucocerebrosidase inhibitors might be used to optimize a lead compound's ability to chaperone the protein in cellulo. The flexibility of this synthetic strategy makes it an attractive approach to the rapid optimization of glycosidase inhibitor potency and pharmacokinetic behavior.

A versatile approach to N-alkylated 1,4-dideoxy-1,4-imino-D-arabinitols and 1,4-dideoxy-1,4-imino-L-xylitols.

A versatile and concise synthesis of N-alkylated 1,4-dideoxy-1,4-imino-D-arabinitol and 1,4-dideoxy-1,4-imino-L-xylitol derivatives is described. These were prepared using pseudohemiketal lactams as key intermediates, which in turn were obtained from sucrose. The key intermediates were prepared by a diastereospecific tandem reaction which facilitated the introduction of various substituents on the nitrogen atom of the iminosugars.

Simultaneous production of 1,3-dihydroxyacetone and xylitol from glycerol and xylose using a nanoparticle-supported multi-enzyme system with in situ cofactor regeneration.

Cofactor-dependent biotransformations often require consumption of a secondary substrate for cofactor regeneration. Alternatively, two synthetic reactions may be coupled together through cofactor regeneration cycles. Simultaneous production of value-added products from glycerol and xylose was realized in this work through an enzymatic NAD(H) regeneration cycle involving two enzymes. Glycerol dehydrogenase (GDH) catalyzed the production of 1,3-dihydroxyacetone (DHA) from glycerol, while xylose reductase (XR) enabled the reduction of xylose to xylitol using the protons released from glycerol. Both enzymes were immobilized with P(MMA-EDMA-MAA) nanoparticles. Interestingly, the immobilized multi-enzyme system showed much improved productivity and stability as compared to native enzymes, such that the total turnover number (TTN) reached 82 for cofactor regeneration while the yield reached 160g/g-immobilized GDH for DHA production.

The optimization of dilute acid hydrolysis of cotton stalk in xylose production.

Cotton stalk, a lignocellulosic waste material, is composed of xylose that can be used as a raw material for production of xylitol, a high-value product. There is a growing interest in the use of lignocellulosic wastes for conversion into various chemicals because of their low cost and the fact that they are renewable and abundant. The objective of the study was to determine the effects of H(2)SO(4) concentration, temperature, and reaction time on the production of sugars (xylose, glucose, and arabinose) and on the reaction by-products (furfural and acetic acid). Response surface methodology was used to optimize the hydrolysis process in order to obtain high xylose yield and selectivity. The optimum reaction temperature, reaction time, and acid concentration were 140 °C, 15 min, and 6%, respectively. Under these conditions, xylose yield and selectivity were found to be 47.88% and 2.26 g g(-1), respectively.

Biodegradable xylitol-based elastomers: in vivo behavior and biocompatibility.

Biodegradable elastomers based on polycondensation reactions of xylitol with sebacic acid, referred to as poly(xylitol sebacate) (PXS) elastomers have recently been developed. We describe the in vivo behavior of PXS elastomers. Four PXS elastomers were synthesized, characterized, and compared with poly(L-lactic-co-glycolic acid) (PLGA). PXS elastomers displayed a high level of structural integrity and form stability during degradation. The in vivo half-life ranged from approximately 3 to 52 weeks. PXS elastomers exhibited increased biocompatibility compared with PLGA implants.

Regioselective reductive cleavage of bis-benzylidene acetal: stereoselective synthesis of anticancer agent OGT2378 and glycosidase inhibitor 1,4-dideoxy-1,4-imino-l-xylitol.

A highly regioselective reductive cleavage of the bis-benzylidene acetal of D-mannitol was performed using a BF(3) x Et(2)O/Et(3)SiH reagent system. A chiral intermediate 6 thus obtained was efficiently utilized in the stereoselective synthesis of the anticancer agent OGT2378 (3) and glycosidase inhibitor derivative N-tosyl 1,4-dideoxy-1,4-imino-L-xylitol (22). Chemoselective reduction of azido epoxide 10 followed by regioselective intramolecular cyclization of amino epoxide 11 resulted in the exclusive formation of deoxyidonojirimycin derivative 12. By changing the order of deprotection, the chiral intermediate 6 was readily transformed to glycosidase inhibitor derivative 22.

Efficient regeneration of NADPH using an engineered phosphite dehydrogenase.

The in situ regeneration of reduced nicotinamide cofactors (NAD(P)H) is necessary for practical synthesis of many important chemicals. Here, we report the engineering of a highly stable and active mutant phosphite dehydrogenase (12x-A176R PTDH) from Pseudomonas stutzeri and evaluation of its potential as an effective NADPH regeneration system in an enzyme membrane reactor. Two practically important enzymatic reactions including xylose reductase-catalyzed xylitol synthesis and alcohol dehydrogenase-catalyzed (R)-phenylethanol synthesis were used as model systems, and the mutant PTDH was directly compared to the commercially available NADP(+)-specific Pseudomonas sp. 101 formate dehydrogenase (mut Pse-FDH) that is widely used for NADPH regeneration. In both model reactions, the two regeneration enzymes showed similar rates of enzyme activity loss; however, the mutant PTDH showed higher substrate conversion and higher total turnover numbers for NADP(+) than mut Pse-FDH. The space-time yields of the product with the mutant PTDH were also up to fourfold higher than those with mut Pse-FDH. In particular, a space-time yield of 230 g L(-1) d(-1) xylitol was obtained with the mutant PTDH using a charged nanofiltration membrane, representing the highest productivity compared to other existing biological processes for xylitol synthesis based on yeast D-xylose converting strains or similar in vitro enzyme membrane reactor systems.

Synthesis of alkylated deoxynojirimycin and 1,5-dideoxy-1,5-iminoxylitol analogues: polar side-chain modification, sulfonium and selenonium heteroatom variants, conformational analysis, and evaluation as glycosidase inhibitors.

The syntheses of N-alkylated deoxynojirimycin and 1,5-dideoxy-1,5-iminoxylitol derivatives having either a D- or an L-erythritol-3-sulfate functionalized N-substituent are reported. The alkylating agent used was a cyclic sulfate derivative, whereby selective attack of the nitrogen atom at the least hindered primary center afforded the desired ammonium salt. In aqueous solution, these salts were configurationally labile at the ammonium center. Sulfonium and/or selenonium analogues of the ammonium salts were prepared by analogous reactions. The chalcogen salts were obtained as mixtures of diastereomers, separable in some cases, differing only in the stereochemistry at the configurationally stable sulfur or selenium atoms. Proof of configuration and conformation of each compound was obtained by detailed NMR experiments. The compounds are six-membered ring analogues of salacinol, a known sulfonium-salt glucosidase inhibitor. Evaluation of the target compounds for enzyme inhibition of the glucosidase enzyme glucoamylase G2 indicated that these compounds were either inactive or, at best, only weak inhibitors of maltose hydrolysis.

Novel perfluoroalkylated derivatives of D-galactopyranose and xylitol for biomedical uses. Hemocompatibility and effect on perfluorocarbon emulsions.

6-O-(4,4,5,5,6,6,7,7,7-Nonafluoro-2-hydroxyheptyl)-, 6-O-(4,4,5,5,6,6,7,7,8,8,9,9,9-tridecafluoro-2-hydroxynonyl)-, and 6-O-(4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,11-heptadecafluoro-2-hydroxyundecyl)-d-galactopyranose (9, 10, and 11, resp.) were prepared by a two-step synthesis including the reaction of 1,2:3,4-di-O-isopropylidene-alpha-d-galactopyranose with 2-[(perfluoroalkyl)methyl]oxiranes under catalysis with BF(3).Et(2)O. Similarly, 1-O-(4,4,5,5,6,6,7,7,7-nonafluoro-2-hydroxyheptyl)-, 1-O-(4,4,5,5,6,6,7,7,8,8,9,9,9-tridecafluoro-2-hydroxynonyl)-, 1-O-(4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,11-heptadecafluoro-2-hydroxyundecyl)-dl-xylitol (18, 19, and 20, resp.) were prepared by a two-step synthesis from the corresponding 1,2:3,4-di-O-isopropylidene-dl-xylitol. Most of the both types of fluoroalkylated carbohydrate derivatives 9-11 and 18-20 generally displayed very low level of hemolytic activity and excellent co-emulsifying properties on testing on perfluorodecalin-Pluronic F-68 microemulsions.